Can someone guide me re possible SULFUR OXIDATION PROBLEM?

So--I have had problems for years-horrible vomiting and nausea from garlic is how it started, but now I can't eat onions, (and everything in garlic and onion family), eggs, dairy, broccoli, and beets. I am very careful to eat organic fruits and veggies, and all grassfed organic etc meats. this all started after a ridiculously long prescription of antibiotics that was based on a misdiagnosis of bronchitis (i'd just moved to NYC and was responding to the air there--allergy meds took it away in two days). ANYWAY i am a health nut and a great cook now because of all of this, so that's the silver lining. However, I"d love to solve this, and I've just come across this stream and related ones re high thios, sulfur oxidation, mercury poisoning etc. It is so much info. Can someone help me? Here's what I've got:

1. do a genetic test on 23andme and then put results through geneticgenie or the other similar website. what am i looking for here?

2. test for mercury. blood? urine? hair? where do i test hair?

3. test for other metals? which?

4. test for cysteine? is that right?

5. is there a probiotic i can take that helps with sulfur oxidation?

6. what do i do if any of these are positive results?

7. is there anything else i should test for?

i extend my gratitude in advance for a comprehensive and organized answer so I can start this part of the process.

ps i went to a western dr who told me my severe bloating was due to swallowing air. I went to a hypnotherapist who specializes in food allergies who told me that i def had a biological problem, not a psychological one. I went to an acupuncturist/chinese herbalist who told me that he found evidence of garlic/onion allergies in ancient texts and there was NO recommendation for it except not to eat them. I have not tried NAET. But I have a feeling that this oxidation thing might be the root of my problems.